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Specify a channel as having premultiplied alpha and use it to un-premultiply all other channels before resampling.

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This commit is contained in:
Jorge Rodriguez
2014-07-31 17:20:00 -07:00
parent a32fa8b4df
commit 8063ea0952
2 changed files with 96 additions and 15 deletions
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45
tests/resample_test.cpp
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@ -91,7 +91,7 @@ int main(int argc, char** argv)
printf("Average: %dms\n", average);
#else
stbr_resize_arbitrary(input_data + w * border * n + border * n, in_w, in_h, w*n, output_data, out_w, out_h, out_stride, s0, t0, s1, t1, n, STBR_TYPE_UINT8, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB, extra_memory, memory_required);
stbr_resize_arbitrary(input_data + w * border * n + border * n, in_w, in_h, w*n, output_data, out_w, out_h, out_stride, s0, t0, s1, t1, n, 0, STBR_TYPE_UINT8, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB, extra_memory, memory_required);
#endif
free(extra_memory);
@ -123,7 +123,7 @@ void resize_image(const char* filename, float width_percent, float height_percen
size_t memory_required = stbr_calculate_memory(w, h, out_w, out_h, 0, 0, 1, 1, n, filter);
void* extra_memory = malloc(memory_required);
stbr_resize_arbitrary(input_data, w, h, 0, output_data, out_w, out_h, 0, 0, 0, 1, 1, n, STBR_TYPE_UINT8, filter, edge, colorspace, extra_memory, memory_required);
stbr_resize_arbitrary(input_data, w, h, 0, output_data, out_w, out_h, 0, 0, 0, 1, 1, n, 0, STBR_TYPE_UINT8, filter, edge, colorspace, extra_memory, memory_required);
free(extra_memory);
stbi_image_free(input_data);
@ -157,7 +157,7 @@ void test_format(const char* file, float width_percent, float height_percent, st
size_t required = stbr_calculate_memory(w, h, new_w, new_h, 0, 0, 1, 1, n, STBR_FILTER_CATMULLROM);
void* extra_memory = malloc(required);
stbr_resize_arbitrary(T_data, w, h, 0, output_data, new_w, new_h, 0, 0, 0, 1, 1, n, type, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, colorspace, extra_memory, required);
stbr_resize_arbitrary(T_data, w, h, 0, output_data, new_w, new_h, 0, 0, 0, 1, 1, n, 0, type, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, colorspace, extra_memory, required);
free(extra_memory);
free(T_data);
@ -201,7 +201,7 @@ void test_float(const char* file, float width_percent, float height_percent, stb
size_t required = stbr_calculate_memory(w, h, new_w, new_h, 0, 0, 1, 1, n, STBR_FILTER_CATMULLROM);
void* extra_memory = malloc(required);
stbr_resize_arbitrary(T_data, w, h, 0, output_data, new_w, new_h, 0, 0, 0, 1, 1, n, type, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, colorspace, extra_memory, required);
stbr_resize_arbitrary(T_data, w, h, 0, output_data, new_w, new_h, 0, 0, 0, 1, 1, n, 0, type, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, colorspace, extra_memory, required);
free(extra_memory);
free(T_data);
@ -267,7 +267,7 @@ void test_subpixel(const char* file, float width_percent, float height_percent,
size_t tempmem_size = stbr_calculate_memory(w, h, new_w, new_h, 0, 0, s1, t1, n, STBR_FILTER_CATMULLROM);
void* tempmem = malloc(tempmem_size);
stbr_resize_arbitrary(input_data, w, h, 0, output_data, new_w, new_h, 0, 0, 0, s1, t1, n, STBR_TYPE_UINT8, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB, tempmem, tempmem_size);
stbr_resize_arbitrary(input_data, w, h, 0, output_data, new_w, new_h, 0, 0, 0, s1, t1, n, 0, STBR_TYPE_UINT8, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB, tempmem, tempmem_size);
free(tempmem);
@ -280,8 +280,43 @@ void test_subpixel(const char* file, float width_percent, float height_percent,
free(output_data);
}
void test_premul(const char* file)
{
int w, h, n;
unsigned char* input_data = stbi_load(file, &w, &h, &n, 4);
n = 4;
// Premultiply the first texel.
input_data[0] /= 2;
input_data[1] /= 2;
input_data[2] /= 2;
input_data[3] = 255 / 2;
int new_w = (int)(w * .5);
int new_h = (int)(h * .5);
unsigned char* output_data = (unsigned char*)malloc(new_w * new_h * n * sizeof(unsigned char));
size_t tempmem_size = stbr_calculate_memory(w, h, new_w, new_h, 0, 0, 1, 1, n, STBR_FILTER_CATMULLROM);
void* tempmem = malloc(tempmem_size);
stbr_resize_arbitrary(input_data, w, h, 0, output_data, new_w, new_h, 0, 0, 0, 1, 1, n, 3, STBR_TYPE_UINT8, STBR_FILTER_CATMULLROM, STBR_EDGE_CLAMP, STBR_COLORSPACE_SRGB, tempmem, tempmem_size);
free(tempmem);
stbi_image_free(input_data);
char output[200];
sprintf(output, "test-output/premul-%s", file);
stbi_write_png(output, new_w, new_h, n, output_data, 0);
free(output_data);
}
void test_suite()
{
test_premul("barbara.png");
for (int i = 0; i < 10; i++)
test_subpixel("barbara.png", 0.5f, 0.5f, (float)i / 10, 1);